You really need a combination of top-down vision combined with bottom-up implementation, mixed together with a healthy dose of pragmatism.
It's enough to know that you'll need lots of gears and to know that you'll need high-capacity mining eventually. But there's no great harm from having a few extra or from having not quite enough to max out beaker production; just start the process, get some gears, get some beakers, and refine as needed. Without a little top-down vision, you'll end up severely overproducing some things and underinvesting in others, which is no good, but you'll never be able to build an optimal factory without first building a suboptimal one.
It's enough to know that you'll need lots of gears and to know that you'll need high-capacity mining eventually. But there's no great harm from having a few extra or from having not quite enough to max out beaker production; just start the process, get some gears, get some beakers, and refine as needed. Without a little top-down vision, you'll end up severely overproducing some things and underinvesting in others, which is no good, but you'll never be able to build an optimal factory without first building a suboptimal one.